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Phosphorus is a growing water quality concern in agricultural landscapes. Sources of agricultural phosphorus include synthetic fertilizers and manure application that support crop growth. These sources lead to excess phosphorus in adjacent waterways causing harm to aquatic communities and to human health. Phosphorus is transported downstream contributing to larger pollution issues including eutrophication of freshwater bodies. Conservation practices called Best Management Practices (BMPs) have been developed to manage agricultural phosphorus pollution. One common BMP is a riparian, or streamside, buffer. This BMP allows for the reestablishment of vegetation between an agricultural field and adjacent waterway. Riparian buffers act as a filter strip and are effective for nitrogen, sedimentation, and erosion control. The efficacy of these practices to manage phosphorus, however, is less clear, notably regarding dissolved phosphorus. Dissolved phosphorus is highly bioavailable and ready for plant uptake, contributing to pollution from rapid algae growth. A saturated buffer is a specific type of riparian buffer known to be effective for nitrogen and particulate phosphorus removal, but in some cases has been shown to contribute to dissolved reactive phosphorus (DRP) pollution. Through field data collection, the aim of this case study was to document DRP contributions from a saturated buffer field research site located in Southern Minnesota. In addition, this study documents the drivers of DRP contributions including soil characteristics, microbial community structure, and flooding. Results from the work demonstrate the need to account for dissolved phosphorus in meeting water quality goals through the implementation of agricultural BMPs. [ABSTRACT FROM AUTHOR]

Black ash wetlands are seriously threatened because of the invasive emerald ash borer (EAB). Wetland hydrology is likely to be modified following ash mortality, but the magnitude of hydrological impact following loss via EAB and alternative mitigation harvests is not clear. Our objective was to assess the water table response to simulated EAB and harvesting to determine if management actions will be needed to maintain ecosystem functions following EAB infestation. We applied four replicated treatments to 1.6 ha plots as follows: (1) control, (2) girdling of all black ash trees to simulate loss via EAB mortality, (3) group selection harvests (20% of stand in 0.04 ha gaps), and (4) clear-cut harvest. Water table (WT) elevations were monitored for 1 year pre-treatment and two years post-treatment. Clear- cutting delayed WT drawdown in both years of the study, and the WT was significantly higher than the control treatment, predominantly when WT depth was below 30 cm. The effect of the group selection treatment on WT response was muted compared to clear-cutting and also limited to periods when the WT depth was below 30 cm. These responses were attributed to establishment of shallowrooted vegetation in cut areas, which would have limited influence on WT dynamics as depth increased. There was little effect of girdling on the WT in the first year post-treatment, but effects on the WT were very similar to clear-cutting in the second year and more pronounced when the WT was within 30 cm of the soil surface. These effects were attributed to reduced transpiration coupled with the presence of a partial canopy following girdling, which would have reduced vegetation establishment and evaporation compared to clear-cutting. Given the large influence of WT depth on vegetation dynamics and associated feedbacks to altered hydrology, these early results indicate a greater risk of ecosystem alteration following EAB mortality compared to clear-cut harvesting. Depending on local hydrologic regime, variation in precipitation patterns, and time for complete canopy loss, it may be necessary for managers to implement active mitigation strategies (e.g., group selection coupled with planting of alternative species) prior to EAB infestation to maintain ecosystem processes in these forested wetland systems. Key words: water table rise, forested wetlands, invasive species, Fraxinus nigra Marshall, forest management, Agrilus planipennis Fairmaire. Les milieux humides occupes par le frene noir (Fraxinus nigra Marshall) sont serieusement menaces a cause de l'agrile du frene (AF) (Agrilus planipennis Fairmaire). Les caracteristiques hydrologiques des milieux humides seront probablement modifiees a la suite de la mortalite du frene mais l'ampleur de l'impact hydrologique cause par les pertes dues a l'AF et les coupes alternatives visant a reduire cet impact n'est pas claire. Notre objectif consistait a evaluer la reaction de la nappe phreatique (NP) a l'action simulee de l'AF et a la coupe pour determiner si des interventions d'amenagement sont necessaires pour maintenir les fonctions de l'ecosysteme a la suite d'une infestation de l'AF. Nous avons applique les quatre traitements suivants que nous avons repetes dans des parcelles de 1,6 ha : (1) temoin, (2) annelation de tous les frenes noirs pour simuler la perte via la mortalite causee par l'AF, (3) coupes de jardinage par groupe (20 % du peuplement par trouees de 0,04 ha) et (4) coupe a blanc. Le niveau de la NP a ete suivi pendant un an avant et deux ans apres les traitements. La coupe a blanc a retarde le rabattement de la NP durant les deux annees de l'etude et elle etait significativement plus haute que dans le traitement temoin surtout lorsque la profondeur de la NP etait inferieure a 30 cm. L'effet de la coupe de jardinage par groupe sur la reaction de la NP etait faible comparativement a l'effet de la coupe a blanc et l'effet etait limite aux periodes durant lesquelles la profondeur de la NP etait inferieure a 30 cm. Ces reactions ont ete attribuees a l'etablissement de vegetation superficiellement enracinee dans les zones coupees, laquelle aurait eu une influence limitee sur la dynamique de la NP a mesure que la profondeur augmentait. L'annelation a eu peu d'effet sur la NP durant la premiere annee apres le traitement mais les effets etaient tres semblables a ceux de la coupe a blanc durant la deuxieme annee et plus prononces lorsque la NP etait a moins de 30 cm de la surface. Ces effets ont ete attribues a la reduction de la transpiration couplee a la presence d'un couvert forestier partiel a la suite de l'annelation, laquelle aurait reduit l'etablissement de la regeneration et l'evaporation comparativement a la coupe a blanc. Etant donne la forte influence de la profondeur de la NP sur la dynamique de la vegetation et les retroactions associees a la modification des caracteristiques hydrologiques, ces resultats preliminaires indiquent qu'il y a un plus grand risque que l'ecosysteme soit modifie a la suite de la mortalite due a l'AF qu'apres une coupe a blanc. Selon le regime hydrologique local, la variation dans le patron des precipitations et le temps necessaire a la disparition complete du couvert forestier, il est possible que les amenagistes doivent mettre en oeuvre des strategies proactives d'attenuation (p. ex. coupe de jardinage par groupe couplee a la plantation d'autres especes) avant une infestation afin de maintenir les processus de l'ecosysteme dans ces milieux humides boises. [Traduit par la Redaction] Mots-cles : elevation de la nappe phreatique, milieux humides boises, espece invasive, Fraxinus nigra Marshall, amenagement forestier, Agrilus planipennis Fairmaire., Introduction The ash genus (Fraxinus) in North America is under threat of extirpation due to the introduction of the invasive emerald ash borer (EAB; Agrilus planipennis Fairmaire), which has decimated [...]

There have been significant increases in stream flow in many rivers of the Upper Midwestern United States since 1980. Increased summer flows may negatively impact ecological processes, including aquatic organisms' life cycles. The smooth soft shell (Apalone mutica) and wood turtle (Glyptemys insculpta) are threatened by alteration of stream flow regime and other changes to river ecosystems in the Upper Midwest. We hypothesized that prolonged duration of high summer flows would reduce time available for nesting. We assessed hydrologic change using the Indicators of Hydrologic Alteration program and stream gauge data, characterized physical properties of sandbars, surveyed turtle nesting sites and assessed historical channel change using aerial photos in GIS on five Upper Midwest rivers. A river stage-sandbar area relationship was developed to determine the effect of prolonged summer flow duration on turtle nesting opportunity for the 1940-2009 time period. Suitable water levels have declined since 1980 in the agricultural watersheds of southern Minnesota likely delaying hatching and reducing survival, particularly for aquatic turtles such as A. mutica. In contrast to the agricultural watersheds, there was no significant change in the northern forested rivers' stream flow and sandbar availability during the nesting season. Management to reduce summer stream flow in agricultural watersheds and protection of known nest sites could benefit threatened aquatic turtle populations. [ABSTRACT FROM AUTHOR]